Biology Exam 3

What is a redox reaction?

there is a reduction and oxidation reaction occuring together

What are electron carriers? Name two examples

compounds that carry electrons and can accept or transfer them, FADH2 and NADH

What are NAD’s oxidized/reduced forms?

oxidized: NAD+

reduced: NADH

What are FAD’s oxidized/reduced forms?

oxidized:FAD (not pos)

reduced:FADH2

What is a reducing agent? What is an oxidizing agent?

reducing agent is a species that reduces the other species. oxidizing agent is the species that oxidizes the other other species

Where does glycolysis take place?

cytoplasm

What is/are the starting molecule(s) in the glycolysis pathway?

glucose

What is/are the end product(s) in glycolysis? How many?

pyruvate (2 per 1 glucose)

Where is energy required? How much is required?

step number 1 (hexokinase) & 3(phosphofructokinase); 1 ATP per step

Where is energy produced? How much is produced (NET)?

step 6 (NADH - dehydrogenase)

step 7 (ATP - phosphoglycercate kinase)

step 10 (ATP - pyruvate kinase)

net ATP- 2, NADH-2, pyruvate- 2

What is the limiting factor in performing cellular respiration in the absence of oxygen?

NAD+

How do cells work around this limitation?

anaerobic respiration (fermentation)

Name and describe the two major types of fermentation.

lactic acid and alcohol

How is NADH oxidized in each of the two types of fermentation?

actic acid - pyruvate gets converted to lactate (NADH oxidized)

alcohol - 2 steps. pyruvate gets converted to acytel. acytel gets converted to alcohol by oxidizing NADH

Where does Oxidation of Pyruvate (OP) take place?

mitochondria

What is the starting molecule of OP?

pyruvate

What is/are the end product(s) of OP? How many?

2 acytel CoA , no ATP, 1 NADH

Where does the citric acid cycle (CA) take place?

matrix of mitochondria

What is the starting molecule of CA?

acytel coA (2 produced but 1 required)

What is/are the end product(s) of CA? How many?

6 -NADH 2 -FADH2 2 -ATP 4 -CO2

Where is energy produced in CA? How much is produced per pyruvate? Per glucose?

Each turn forms 3 NADH (isocitric acid to a-ketoglutaric acid; a-ketoglutaric to succinyl CoA; Malate to oxaloacetate), 1 FADH2 (Succinate to Fumerate), and 1 ATP(Succinyl CoA to Succinate) per pyruvate. times two per glucose.

What is the benefit of having a cyclical step in cellular respiration?

each time the reactant will be regenerated (oxaloacetate and acytel coA

Describe the complexes making up the ETC. How many protein complexes are there?

group of complexes passing on the electrons to oxygen to form water

4 protein complexes

Where does the ETC take place?

mitochondrial inner membrane (cristaes) in eukaryotes. prokaryotes in plasma membrane

What is/are the waste product(s)?

water

How do the different electron carrier molecules interact with the ETC

by donating their high-energy electrons, which then move through a series of protein complexes on the inner mitochondrial membrane

What direct role does oxygen play?

oxygen is getting reduced (gaining electrons) and becomes water

What is the purpose of the reduction and subsequent oxidation of all the electron carrier molecules? What happens to them after they have served their purpose?

electron carrier molecules include NADH and FADH2 produce ATP

they get recycled when they are done with their purpose

What is the energy from the redox reactions in the electron transport chain used to do?

used to do work like transporting protons

What is chemiosmosis? How does it transfer energy? What ions are involved?

when ions move across the concentration gradient (osmosis of chemicals). transfers energy using ATP Synthase

Chemiosmosis is the process where ions, primarily protons, move across a semipermeable membrane down an electrochemical gradient to generate ATP. It transfers energy by using the potential energy stored in this proton gradient to power the enzyme ATP synthase, which phosphorylates ADP to create ATP. The main ion involved is the hydrogen ion.

Where does the chemiosmotic gradient occur in eukaryotic cells?

inner membrane of mitochondria

How do the protons move back across the membrane?

ATP synthase

How is the energy transferred to ATP?

uses proton gradient

What is the theoretical energetic yield of cellular respiration?

38 ATP

What is a more realistic estimate of energy yield?

32

Why is there such variation in the amount of energy actually made?

transfer of the molecules can be inefficient due to varying number of hydrogen ions and other intermediate molecules

Why do you think cellular respiration needs to be regulated

1. provide balance amounts of energy in the form of ATP without being wasteful

2.to utilize and generate other molecules

How are non-glucose carbohydrates, proteins, and lipids used as sources of energy?

broken down into smaller molecules that feed into glycolysis or directly into the citric acid cycle as intermediates like acetyl-CoA or pyruvate (aerobic)

What are specific examples of how cellular respiration is regulated?

feedback inhibition; By proteins which transport glucose into the cell; By the number and specificity of the glycolysis, oxidation, fermentation, citric acid cycle, etc. enzymes; By the presence of coenzymes, cofactors, competitive & allosteric inhibitor

What are two specific examples of feedback inhibition on the rate of cellular respiration

feedback inhibition: phosphofructokinase in glycolsis uses ATP to inhibit enzymes,

in electron transport chain, high levels of ATP slows down ETC, while high levels of ADP speeds it up

What are the four major steps of cellular respiration?

Glycolsis, oxidation of pyruvate, citric acid cycle, ETC

Which of the four steps require oxygen? Which do not?

electron transport chain (O2 is major molecules that takes electron at the end). Krebs and pyruvate oxidation require it INDIRECTLY

Cellular respiration

Cellular respiration is a biochemical process in which cells convert glucose (or other food molecules) into usable energy (ATP). This process uses oxygen (in most cases) and releases carbon dioxide and water as byproducts.

Oxidation

loss of electrons

reduction

gain of electrons

Chemiosmosis

osmosis of ions

aerobic

requiring oxygen

anaerobic

not requiring oxygen

fermentation

converts NADH to NAD+ (oxidizes) so that it can be used in glycolysis.

Photoautotrophs

create their own food using light

Heterotrophs

take energy from photosynthatic organisms (cant make own food)

Chemoautotrophs

make food from chemicals

Photosynthetically active radiation

range that pigments can absorb- 400nm -700nm

Absorption spectrum

the identity of each pigment

Name two major classes of pigments that absorb lights in plants

chlorophyll and carotenoid

Relate the concept of the absorption spectrum of pigments with the green color of most plant tissue

because they reflect green and absorb the rest of the pigments

Stomata

Gas exchange (intake of CO 2 and release of O 2 ) occurs through small openings called stomata (singular: stoma). Stomata also aid in water balance

guard cells

found on either side of a stoma, and regulate the opening and closing

thylakoid

contain chlorophyll , a pigment, or molecule that absorbs light

granum

stacks of thylakoid

stroma

liquid present inside of chloroplast

Name the general tissue in the leaf where photosynthesis takes place

mesophyll

How are gases (CO2 and O2) exchanged through the surface of the leaf

using the stomata

Be able to describe in detail the structure of the organelle where photosynthesis takes place in eukaryotes

outer membrane, inner membrane, Stomata, thylakoid, granum, stroma, guard cells

Name the three reactants required for photosynthesis

sunlight, water, CO2

Name the two basic products of photosynthesis.

Glucose, O2

Understand the differences between the light- dependent and light-independent reactions of photosynthesis.

dependent requires light energy, independent does. Dependent occurs in thylakoid while independent is in stroma

Where does the light-dependent reaction take place? light independent?

thylakoid membrane; stroma

What are the major products of the light- dependent reaction?

ATP, NADPH, and O2

What are the major products of the light- independent reaction?

GA3P, ADP, Pi, NADP+

Describe the parts of a photosystem.

1. light harvesting complex : 300-400 chlorophyll molecules (and other pigments) bound to antenna proteins

2. reaction center:A specialized pair of chlorophyll- a molecules capable of being oxidized

What is so unique about what happens during a “photoact?”

The energy is passed to a special chlorophyll- a pair, and that electron is passed to the primary electron acceptor. it turns light energy to chemical energy in an excited electron in PS II

In Photosystem II, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?

water molecule

In Photosystem I, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?

etc

Where does the high energy electron go after it leaves Photosystem II?

NADPH

What is the waste product produced from Photosystem II? other products?

O2; ATP and NADPH

What is the purpose of Photosystem I?

at the end, so gives up electron to NADPH and re energize electron using a photon

What are the products of Photosystem I?

NADPH and ATP

Understand what the energy derived from the electron transport chain is used for in plants

to generate chemical energy in the form of ATP and NADPH

Where in the chloroplast is the chemiosmotic gradient established?

thylakoid lumen and stroma

What is the hydrogen ion gradient potential energy used for? How is it harnessed?

The potential energy from a hydrogen ion gradient is primarily used for ATP synthesis, a process called chemiosmosis. This energy is harnessed by an enzyme called ATP synthase. As hydrogen ions flow down their electrochemical gradient through ATP synthase, they power the enzyme to attach a phosphate to ADP, producing ATP, the cell's main energy currency. 

What is the captured chemical energy (ATP and NADPH) used for during photosynthesis?

to power the Calvin cycle

Where does the carbon come from that is used to build carbohydrates in the light-independent reaction of photosynthesis?

CO2 - inorganic molecule

Describe what happens in each of the three major stages of the Calvin-Benson Cycle.

Fixation: enzyme RuBisCO catalyzes a reaction between CO2 and a 5 carbon sugar called RuBP resulting in two intermediate molecules (3-PGA). Called fixation because carbon is fixed from an inorganic form (CO2) into an organic form (3-PGA)

Reduction: ATP and NADPH form light-dependent reactions that reduce 3-PGA into G3P using ATP and NADPH. once oxidized, ADP and NADP+ are recycled back to light-dependent reactions.

Regeneration: remaining G3P are used to regenerate RuBP using ATP so the cycle can continue. Some G3P leaves cycle and enters cell cytoplasm to contribute to the formation of glucose

What is the enzyme that plants use for carbon fixation?

RuBisCO

What is the name of the high-energy 5-carbon molecule carbon is fixed to

RuBP

What is the name of the molecule formed by carbon fixation?

3-phosphoglyceraldehyde (3-PGA)

What is the name of the molecule formed by the reduction of 3-PGA? what is the fate of this product?

G3P (5 continue to regenerate RuBP and one leaves from chloroplast to cytoplasm to form other molecules)

Why do plants need adaptations in the photosynthetic pathways?

to help high water loss and high temperature

What is the name of the undesirable “alternate” pathway that occurs in the light-independent pathway?

photorespiration

What enzyme causes the problem, and why does this occur?

RuBisCO, because O2 acts as inhibitor of this enzyme

Under what conditions does photorespiration usually occur?

in presence of abundant O2

Why is photorespiration so detrimental to the plant?

results in releasing CO2, undoing CO2 fixation

What enzyme do C4 plants use in place of RuBisCo?

Pep Carboxylase

What are the benefits of using PEP Carboxylase instead of RuBisCo?

not inhibited by abundance of O2

What is the name of the molecule that carbon is first fixed to in C4 plants

PEP to create oxaloacetate (4 carbon)

How do C4 plants use spatial separation of the light- independent process to overcome photorespiration?

O2 can only build up in mesophyll cells and RuBisCO is only present in bundle sheath cells. This creates a high CO2 to O2 ratio around RuBisCO, minimizing its oxygenase activity and therefore suppressing photorespiration. 

What are the costs associated with performing C4- type photosynthesis?

2 ATPs required for 1 CO2, 12 ATPs for 1 glucose

How do CAM plants avoid photorespiration?

they perform the first step using PEP carboxylase during the night, and perform the other step using RuBisCO during the day (temporal separation)

Which enzymes do CAM plants use to initially fix carbon?

PEP carboxylase